DE19948850A1 - Thermoformable polyamides - Google Patents

Abstract

The invention relates to glass-fiber reinforced polyamides and to the use thereof for thermoforming.

Description

The invention relates to glass fiber reinforced polyamides and the use of these for Thermoforming.

The thermoforming of thermoplastic semi-finished products has in the past Gained an increasingly important status over the years. Not least the possibility Developing prototypes quickly offers advantages over more complex con competition, such as injection molding. Constantly improved thermoplastics allow an increase in quantities with modern machines and tools performance with simultaneously increased precision of the molded parts (Kunststoff-Handbuch 3/4 "Polyamides", Hanser Verlag Munich, Vienna).

Hitherto largely excluded from thermoforming applications (thermoforming in The practice, S. 45 ff, Hanser Verlag, Munich, Vienna) were from the group of semicrystalline thermoplastics the polyamides and especially the reinforced Polyamides. The very narrow processing window of this class of material, the one Forming allowed only shortly below the crystallite melting point and by the low melt viscosities caused inadequate melt level These polymeric materials allowed the transformation of these materials Semi-finished products (plates) only to very flat thermoformed parts with low Ver degree of stretching and low Ausformschärfe.

The thermoforming of films, also often referred to as deep drawing, is for polyamide (single-layered, multi-layered, coextruded or laminated) (packaging with plastics, Hanser Verlag, Munich, Vienna). Of films for thermoformers The expert speaks at a film thickness of less than 1500 μm (Thermo forms, Hanser Verlag, Munich, Vienna, 1999).

It was therefore the object to provide a reinforced polyamide, from the thermoplastic semi-finished product with a material thickness of greater than 1.5 mm  can be made from which then in the thermoforming moldings with high degree of deformation and good Ausformschärfe can be produced.

Surprisingly, it was found that polymeric materials from the Material class of pseudoplastic reinforced polyamides, as z. In EP-A 0 685 528 are described, with inventive viscosity behavior itself very good for thermoforming use. It could reach degrees of deformation be achieved with previously known materials by far. The Materials show a large forming temperature range.

These molding compounds are characterized by their clear pseudoplastic behavior in the Compared to standard polyamides. That is, these molding compounds have a significantly higher viscosity at low shear rates compared to Standard polyamides and comparably high viscosities at high shear rates on. This intrinsic viscosity is achieved by increased desulfurization Degree of these polyamides. This can be used for primary condensation in the so-called VK pipe or in a subsequent com poundierung.

The reinforcement of polyamides is known to occur by the incorporation of z. As glass fibers or mineral fillers in the polyamide melt z. B. off an extruder.

The invention therefore relates to reinforced polyamide molding compositions whose viscosity is greater than 1000 Pa.s at a shear rate of 10 s ^-1 and less than 300 Pa.s at a shear rate of 1000 s ^-1 , at a processing temperature of 40 up to 80 ° C above the melting point of the molding material concerned.

Preferred are reinforced polyamide molding compositions whose viscosity at a shear rate of 10 s ^-1 greater than 1500 Pa.s and at a shear rate of 1000 s ^-1 less than 280 Pas, at a processing temperature of 40 to 80 ° C above the melting point , which is the relevant molding material.

Another object is the use of these molding compositions according to the invention for thermoforming.

The use of molding compositions is preferred

• A) 98 to 41 parts by weight of thermoplastic semicrystalline polyamide and
• B) 2 to 50 parts by weight of reinforcing materials
• C) 0.1 to 4 parts by weight of branching and / or molecular weight increasing Additives, e.g. B. diepoxide
• D) 0 to 5 parts by weight of further additives, for. B. Processing additives for Thermoforming, colorants, carbon blacks,

the sum of the parts by weight A, B, C and D together being 100,
for thermoforming.

Particularly preferred is the use of molding compositions containing

• A) 67 to 85 parts by weight of thermoplastic semicrystalline polyamide and
• B) 15 to 30 parts by weight of reinforcing materials
• C) 0.2 to 1 part by weight of branching and / or molecular weight increasing Additives, e.g. B. diepoxide
• D) 0.1 to 2 parts by weight of further additives, for. B. Processing additives for Thermoforming, colorants, carbon blacks,

the sum of the parts by weight A, B, C and D together being 100,
for thermoforming.

Another object of the application are thermoformed moldings, available from the described molding compositions used.

Suitable thermoplastic polyamide A) are semicrystalline polyamides (PA), preferred are PA 6, PA 66, PA 46, PA 610 PA 6 / 6T or partially crystalline copoly amides or mixtures based on these components.

The class of polyamides is described in the Kunststoff-Handbuch 3/4 "Polyamides" Hanser Verlag, Munich, Vienna. This concerns in particular the Her position of the base resins (chapter 2.1), as well as their modification (chapter 2.3) as well as the Reinforcement (chapter 2.4).

For the preparation of polyamides, a variety of procedures are known become, whereby depending upon desired end product different Monomerbau stones, various chain regulators for setting a desired Molekularge or monomers with reactive groups for later intended treatments are used.

The technically relevant processes for the production of polyamides are running out without exception via the polycondensation in the melt. In this framework will too the hydrolytic polymerization of lactams understood as polycondensation.

Preferred polyamides for the molding compositions according to the invention are partially crystalline Polyamides derived from diamines and dicarboxylic acids and / or lactams with at least 5 ring members or corresponding amino acids can.

The starting materials are preferably aliphatic dicarboxylic acids such as Adi formic acid, 2,2,4- and 2,4,4-trimethyl adipic acid, azelaic acid, sebacic acid, alipha diamines such as hexamethylenediamine, 2,2,4- and 2,4,4-trimethylhexamethylene diamine, the isomeric diamino-dicyclohexylmethane, diamino-dicyclohexylpropane,  Bis-aminomethyl-cyclohexane, aminocarboxylic acids such as aminocaproic acid, or the corresponding lactams into consideration. Copolyamides of several of the above Monomers are included.

Particularly preferred are caprolactams, most preferably ε-caprolactam used.

Polyamide 6 and / or polyamide 6,6 are particularly preferably used. All Polyamide 6 is particularly preferred.

The polyamides prepared according to the invention may also be mixed with others Polyamides and / or other polymers are used.

As reinforcing materials B) are commercially available glass fibers, carbon fibers, Mineral fibers, fillers with or without surface treatment etc. for polyamides, used singly or in mixtures. Preferred fibrous or particulate Fillers and reinforcing materials are glass fibers, glass beads, glass fabrics, Glass mats, aramid fibers, carbon fibers, potassium titanate fibers, natural fibers, amorphous silica, magnesium carbonate, barium sulfate, feldspar, mica, Silicates, quartz, kaolin, talc, titanium dioxide, wollastonite, and the like. a., which also has surfaces can be treated. Particularly preferred reinforcing materials are commercial usual glass fibers. The glass fibers, which generally have a fiber diameter between 8 and 18 microns, can as continuous fibers or as cut or ground glass fibers are added, the fibers with a suitable Sizing system and a bonding agent or bonding agent system z. B. on Silane base can be equipped.

As branching additives C) for the molding compositions according to the invention z. B. Commercially available diepoxides, based on diglycidyl ether, (bisphenol A and epichloro hydrine), based on amine epoxide resins (aniline and epichlorohydrin), based on digly cidyl esters (cycloaliphatic dicarboxylic acids and epichlorohydrin) individually or in  Mixtures, and preferably diexpoxides based on 2,2-bis [p hydroxy-phenyl] -propane-diglycidyl ether, bis [N-methyl-N-2,3-epoxypropylamino phenyl] -methane.

As component D, conventional additives, such as agents against heat decomposition, Anti-thermal agent, anti-ultraviolet agent Light, plasticizer, lubricants and mold release agents, nucleating agents, stabilizers ren and dyes and pigments are used.

As examples of antioxidants and heat stabilizers are sterically gehin phenols and / or phosphites, hydroquinones, aromatic secondary amines such as Diphenylamines, various substituted representatives of these groups and theirs Mixtures in concentrations up to 1 wt .-%, based on the weight of called thermoplastic molding compositions.

As UV stabilizers, which are generally in amounts of up to 2 wt .-%, based on the molding materials used are various substituted resorcinols, sali cylates, benzotriazoles and benzophenones.

There may be inorganic pigments such as titanium dioxide, ultramarine blue, iron oxide and Carbon black, furthermore organic pigments, such as phthalocyanines, quinacridones, perylenes and dyes, such as anthraquinones as colorants and other colorants added be set.

As a nucleating agent z. Sodium phenylphosphinate, alumina, Silica and preferably talc are used.

Lubricants and mold release agents, which are usually present in amounts of up to 1% by weight are preferably ester waxes, peterithritol stearate (PETS), long chain fatty acids (eg stearic acid or behenic acid), their salts (eg  Zn stearate) and amide derivatives (eg., Ethylene bis-stearylamide) and niedermole cellular polyethylene or polypropylene waxes.

Under thermoforming (thermoforming) is in this application a Produktionsver driving understood in which a thermoplastic film or plate until Erwei heated, at a low pressure in a tool deformed, cooled and post-processed. All thermoplastics that can be produced as a foil or plate, are in principle also thermoformable with the restriction that the temperature of the Heat resistance of the material does not exceed. The inherent strength should be sufficient to prevent excessive sagging to the breaking of the film or Prevent plate. The thickness range of freely thermoformable semi-finished products goes from 0.1 mm thick films up to 10 mm thick plates (Kunststoff Handbuch 3/4 "Polyamides", Hanser Verlag Munich, Vienna p. 459, 460.

During thermoforming, the heated semi-finished product only comes into contact on one side with the mold. On the investment side of the semi-finished product, the upper surface contours of the mold accurately shown. The contour and also the Dimensions on the other side of the formed part result in the result wall thickness of the thermoformed part. In principle, between positive and negative deformation, depending on whether the inside or outside the molded part comes to rest with the mold. Corresponding results in the shape accuracy of the inner contour (positive deformation) or the Outer contour (negative deformation) of the molding.

The main advantages of thermoforming are cost-effective thermoforming tools, cheaper thermoforming machines, the possibility of even multi-layer materials, foams and pre-printed semi-finished products ("Thermo Forms in Practice ", Schwarzmann, P., Hanser Verlag, Munich, Vienna, 1997).  

Examples and Comparative Examples

The assessment of the quality of the thermoformed articles was made on the following characteristics:

• - Forming and drawing degree
  The degree of uniformity is the ratio between the maximum draw depth H and the width B or the diameter D of the forming surface (clear width of the clamping frame surface).
  The degree of stretching is the ratio between the surface of the molded part before the trimming (without clamping edge) to the molding surface.
• - Thermoformability
  The shaping behavior is assessed. The plate-shaped semi-finished product should have sufficient strength with low sag in the tenter during the heating phase and can be easily deformed by the tool, without thereby forming melt overhangs and wrinkles. The evaluation is done with grades (1 = very good, 6 = insufficient).
• - Wall thickness distribution
  The wall thickness of the individual stages of Herge with the step tool Herge thermoformed parts is measured and assessed the uniformity. This is determined by the arithmetic mean of the individual values of the levels, as well as the maximum deviation from the mean based on the mean value. The evaluation is done with grades (1 = very good, 6 = insufficient).
• - Ausformschärfe
  Under the Ausformschärfe means the accuracy of Kon the curves of the thermoforming mold on the molding. As criteria, mainly small radii and surface structures are observed on the plant side to the tool.
  It was judged the shape in the corner area. The evaluation was made on the basis of grades (1 = very good shape to 6 = insufficient shape).

There are thermoforming parts of the material used in the invention and Comparative material prepared and judged confronting.

The following products are used:
PA 6: Durethan® B 31 from Bayer AG (relative solution viscosity: 3, measured in 1% meta-cresol solution at 25 ° C.)
Diepoxid: Rutapox 0162 from Bakelite AG (diepoxide based on bisphenol A and epichlorohydrin)
Glass fiber: CS 7923 of Bayer AG, Leverkusen, Germany
Additives: nucleating agent (microtalk)
Heat Stabilizer (CuJ / Alkali Halides)
soot

Example B1

On a twin-screw extruder (ZSK) from Werner & Pfleiderer (100 min ^-1 , 10 kg / h), the components listed below were compounded at 265 ° C., extruded into a water bath and granulated. The diepoxide was metered with a liquid metering pump in the catchment area of the extruder.

designation Wt .-% PA6 84.0 glass fiber 15.0 diepoxide 0.5 additives 0.5

Comparative Example VB1

On a twin-screw extruder from Werner & Pfleiderer (100 min ^-1 , 10 kg / h), the components listed below were compounded at 265 ° C., extruded into a water bath and granulated.

designation Wt .-% PA 6 84.5 glass fiber 15.0 additives 0.5

Example B2

On a twin-screw extruder from Werner & Pfleiderer (100 min ^-1 , 10 kg / h), the components listed below were compounded at 265 ° C., extruded into a water bath and granulated. The diepoxide was metered with a liquid metering pump in the catchment area of the extruder.

designation Wt .-% PA 6 68.8 glass fiber 30.0 diepoxide 0.5 soot 0.2 additives 0.5

Comparative Example VB2

On a twin-screw extruder from Werner & Pfleiderer (100 min ^-1 , 10 kg / h), the components listed below were compounded at 265 ° C., extruded into a water bath and granulated.

designation Wt .-% PA 6 69.3 glass fiber 30.0 soot 0.2 additives 0.5

The granules obtained were in each case at about 70 ° C in a vacuum oven 4 Hours dried.

The melt viscosities of the polymers thus prepared were then on a capillary rheometer (DIN 54811-B) for different shear rates and temperatures determined. The measured values were in each case in the true shear rates and true viscosities. The The following table gives the comparison for three shear rates at one Melting temperature of 6 m = 280 ° C (melting point PA about 220 ° C) again.

Table 1

The production of the required semi-finished sheet was done with the example prepared granules on an extrusion line. The polymer granules were thereby extruded through a vented extruder through a slot die and over a calender removed and calibrated. There were so plates with 3 mm thickness and 800 mm in width, which were cut to about 1100 mm in length.

The plate semi-finished products were then applied to a thermoforming system from Illig (type Illig UA 100 Thermoform plant) thermoformed. As thermoforming tool (TW) a rectangular step tool was used, which allows different Material behavior easy to judge. The used stage tool allows the setting of different drawing depths, by varying the number of steps (3 Steps / 5 steps / 7 steps). The single step height is 30 mm each.

In each case the thermoformability, the wall thicknesses and the Shape sharpness for set stretch listed in the following table grade.

Table 2

The result with those produced from the example extruded plates Thermoformed parts are given in the following table:  

Table 3

From Table 3 it can be seen that the inventive Erfrndungsgemäßen better Thermoformability, wall thickness distribution and Ausformschärfe have.

The thermoforming was carried out at set surface temperatures of T = 235 ° C to 254 ° C for B1 and B2, and T = 225 ° C to 230 ° C for VB1 and VB2.

Claims (6)

1. Reinforced polyamide molding compounds whose viscosity at a shear rate of 10 s ^-1 greater than 1400 Pa.s and at a shear rate of 1000 s ^{-1 is} less than 300 Pa.s, at a processing temperature of 40 to 80 ° C above the Melting point of the molding compound in question. 2. Reinforced polyamide molding compounds whose viscosity at a shear rate of 10 s ^-1 greater than 1500 Pa.s and at a shear rate of 1000 s ^{-1 is} less than 280 Pa.s, at a processing temperature of 40 to 80 ° C above the Melting point of the molding compound in question. 3. Use of the molding compositions according to claim 1 and / or 2 for thermo to form. 4. Use of reinforced molding compositions containing

• A) 98 to 41 parts by weight of thermoplastic semicrystalline polyamide and
• B) 2 to 50 parts by weight of reinforcing materials
• C) 0.1 to 4 parts by weight of branching and / or molecular weight-increasing additives, for. B. diepoxide
• D) 0 to 5 parts by weight of further additives, for. B. Processing additives for thermoforming

the sum of the parts by weight A, B, C, D together being 100,
for thermoforming. 5. Use of reinforced molding compositions containing

• A) 67 to 85 parts by weight of thermoplastic semicrystalline polyamide and
• B) 15 to 30 parts by weight of reinforcing materials
• C) 0.2 to 1 parts by weight of branching and / or molecular weight-increasing additives, for. B. diepoxide
• D) 0.1 to 2 parts by weight of further additives, for. B. Processing additives for thermoforming

the sum of parts by weight of A, B, C, D together being 100, for thermoforming. 6. Shaped body obtainable according to one or more of the preceding Claims.